water pressure at RO/DI unit

[Wade]

I installed my new RO/DI system and the water pressure flowing through it is 30 psi. The water pressure in my house is 50. I installed the unit in the laundry room and I'm using a y-adapter to split the cold water supply for the washing maching to feed the RO/DI unit. I know there are pumps to increase water pressure, but can they raise it from 30 to the 50 I need? Any suggestions?

[NonSequitur]

That's odd that the pressure at the unit is lower than the pressure in the rest of the house. Are you measuring the pressure at the inlet of the system, or after filters, etc? If you decide to go with a booster pump you shouldn't have trouble finding one that can provide at least 50psi. For example, bulk reef supply sells an Aquatec 8800 booster pump that can be adjusted to produce up to 160psi, though most membranes shouldn't be run that high:

http://www.bulkreefsupply.com/store/products/reverse-osmosis-filters-and-systems/ro-di-accessories/aquatec-8800-booster-pump-kit.html

Feeding the membrane with a higher inlet pressure will increase both the quantity and purity of product water, and reduce waste by allowing the membrane to run at peak efficiency.

[Wade]

Actually I'm just looking at the pressure gauge on the RO/DI unit. I don't have any other means of checking the pressure. I suppose I could buy a gauge and fit it to connect to the washer outlet. Maybe I'll do that tomorrow to see what i get. If the pressure is good going into the RO/DI, but is only reading 30 what does that mean? The unit and filters are new so they shouldn't be clogged. The water barely trickles out of the DI filter.

[afgun]

My RODI was running about 45 PSI at the membrane. When I added a second piggyback membrane, water pressure dropped to 35 PSI. I think there's a problem with the housing. But I got dissatisfied with the vendor... Not nearly enough pressure to be efficient. I'm now running a single membrane from BFS with an 8800 booster pump. It can easily get a 75 GPD membrane up to 90 PSI (which I think is the max recommended pressure). The pump can be had for about $120. The transformer is about $25. You'll probably want a pressure shutoff switch, which is probably another $20. You can reuse your existing auto-shutoff if you have one (doing this now) or switch to an electric cutoff switch, which I have on order.

[Wade]

Well I tested my pressure before and after the two pre-RO filters (sediment and charcoal). The pressure before is 110 psi and the pressure after the filters is roughly 32 psi. Do the filters constrict the flow that much? Is that why everyone has to run a booster pump after the filters before it goes into the RO membrane or is there something wrong with my housing?

[Wade]

I noticed that if I close the flush valve about half way that my water pressure increases quite a bit. Am I supposed to run it with the flush valve wide open or should I adjust it to get optimum presure and output? Also, my DI canister only has a couple of inches of water in it. That's the most it will fill. My output is at a fast trickle with the flush valve about half closed. BTW, the waste output hose has a "Y" connector with a flush valve on top and a tube with a restricter built into it on the bottom.

Edited March 5, 2011 by Wade

[afgun]

Your flush valve should only be open when flushing the system; otherwise it should be closed, forcing all waste water through the flow restrictor. You may have to adjust your restrictor so that you get a 4:1 waste:permeate flow rate.

Don't worry about low water in your DI media; it will fill up over time.